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United States Patent |
5,741,846
|
Lohmeijer
,   et al.
|
April 21, 1998
|
Thermoplastic composition comprising a compatibilizer polyphenylene
ether polyamide base resin and electroconductive carbon black
Abstract
The present invention deals with a thermoplastic composition comprising (a)
a compatibilized polyphenylene ether-polyamide base resin, and (b) 1-7
parts by weight per 100 parts by weight of (a) of an electroconductive
carbon black, with an Izod notched impact strength of more than 15
kJ/m.sup.2 and a volume resistivity of less than 10.sup.6 Ohm.multidot.cm.
Inventors:
|
Lohmeijer; Johannes Hubertus Gabriel Marie (Hoogerheide, NL);
Fortuijn; Johannes Everardus (Bergen op Zoom, NL);
Wagenaar; Jan (Bergen op Zoom, NL)
|
Assignee:
|
General Electric Company (Pittsfield, MA)
|
Appl. No.:
|
617535 |
Filed:
|
March 15, 1996 |
Foreign Application Priority Data
Current U.S. Class: |
524/538; 252/511; 524/540; 525/397 |
Intern'l Class: |
C07K 003/16 |
Field of Search: |
524/538,540
525/397
252/511
|
References Cited
U.S. Patent Documents
3257357 | Jun., 1966 | Stamatoff | 528/215.
|
3257358 | Jun., 1966 | Stamatoff | 528/212.
|
3306874 | Feb., 1967 | Hay | 528/215.
|
3306875 | Feb., 1967 | Hay | 528/215.
|
4329276 | May., 1982 | Reardon | 524/502.
|
4329278 | May., 1982 | Reardon | 524/523.
|
4388607 | Jun., 1983 | Toy et al. | 338/225.
|
4391741 | Jul., 1983 | Masamoto et al. | 252/511.
|
4929388 | May., 1990 | Wessling | 252/500.
|
5143650 | Sep., 1992 | Gerace et al. | 524/496.
|
5223106 | Jun., 1993 | Gerace et al. | 204/181.
|
5250226 | Oct., 1993 | Oswal et al. | 252/500.
|
5256574 | Oct., 1993 | Neuburger et al. | 436/143.
|
5322874 | Jun., 1994 | Fujii et al. | 524/495.
|
5334636 | Aug., 1994 | Fujii et al. | 525/68.
|
Foreign Patent Documents |
0506386 | Sep., 1992 | EP.
| |
Primary Examiner: Krass; Frederick
Parent Case Text
This is a continuation of application Ser. No. 08/349,850 filed on Dec. 6,
1994, now abandoned.
Claims
We claim:
1. A thermoplastic composition comprising (a) a compatibilized
polyphenylene ether-polyamide base resin, and (b) 1-7 parts by weight per
100 parts by weight of (a) an electroconductive carbon black, wherein the
composition has a notched Izod impact strength of more than 15 kJ/m.sup.2
(measured in accordance with ISO 180/1A) and a volume resistivity of less
than 10.sup.6 Ohm-cm (measured on the narrow parallel portion of a
multipurpose test specimen type A according to ISO 3167 with a length of
about 70 mm obtained by breaking off both ends of the test specimen,
molded as described in ISO 294 for dumb-bell bars, the fracture surface of
both ends being coated with a silver paint and the resistivity being
measured between the silver painted surfaces with an electrical
multimeter) and wherein said electroconductive carbon black is added into
said compatibilized polyphenylene ether-polyamide base resin.
2. A composition as in claim 1, wherein the composition has a volume
resistivity of less than 5.times.10.sup.5 Ohm.multidot.cm.
3. A composition as in claim 1, wherein the composition has a volume
resistivity of between 5.times.10.sup.3 and 5.times.10.sup.5
Ohm.multidot.cm.
4. A composition as in claim 1, comprising 2-5 parts by weight of
electroconductive carbon black per 100 parts by weight of (a).
5. A composition as in claim 1, wherein the composition has a melt
viscosity of less than 260 Pa.multidot.s, as determined in accordance with
ISO 1133 at 1500 s.sup.-1 and 282.degree. C.
6. A composition as in claim 1 wherein said compatibilized base resin (a)
is comprised of (a.sub.1) 10 to 90 weight percent polyphenylene ether
resin and (a.sub.2) 90 to 10 weight percent polyamide resin, based upon
the weight of (a.sub.1) and (a.sub.2) together.
7. A composition as in claim 6 wherein said polyamide resin constitutes a
continuous phase in an amount greater than 35 weight percent of the
compatibilized base resin (a).
8. A composition as in claim 1 comprising a compatibilizing agent selected
from the group consisting of: maleic anhydride, fumaric acid, citric acid,
malic acid, reaction products of a polyphenylene ether and trimellitic
anhydride acid chloride and reaction products of a polyphenylene ether and
maleic anhydride or fumaric acid.
9. A composition as in claim 1 wherein said polyphenylene ether resin is a
polymer or copolymer comprised of one or more units derived from compounds
selected from the group consisting of 2,6-dimethyl phenol and
2,3,6-trimethyl phenol, and wherein said resin has an intrinsic viscosity
of 0.25 to 0.6 dl/g as measured in chloroform at 25.degree. C.
10. A composition as in claim 9 wherein said polyphenylene ether is
poly(2,6-dimethyl-1,4-phenylene ether).
11. A composition as in claim 1 wherein said polyamide resin is selected
from the group consisting of polyamide 6 and polyamide 6,6.
12. A composition as in claim 1 which comprises an agent to improve the
impact strength.
13. The composition of claim 1, further comprising an additive selected
from the group consisting of reinforcing fibers, stabilizers, dyes,
pigments, polyolefins, lubricants and mixtures thereof.
14. An article comprising the composition of claim 1.
15. A thermoplastic composition consisting essentially of (a) a
compatibilized polyphenylene ether-polyamide base resin, and (b) 1-7 parts
by weight per 100 parts by weight of (a) an electroconductive carbon
black, wherein the composition has a notched Izod impact strength of more
than 15 kJ/m.sup.2 (measured in accordance with ISO 180/1A) and a volume
resistivity of less than 10.sup.6 Ohm-cm (measured on the narrow parallel
portion of a multipurpose test specimen type A according to ISO 3167 with
a length of about 70 mm obtained by breaking off both ends of the test
specimen, molded as described in ISO 294 for dumb-bell bars, the fracture
surface of both ends being coated with a silver paint and the resistivity
being measured between the silver painted surfaces with an electrical
multimeter) and wherein said electroconductive carbon black is added into
said compatibilized polyphenylene ether-polyamide base resin.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to thermoplastic compositions comprising (a) a
compatibilized polyphenylene ether-polyamide base resin, and (b) 1-7 parts
by weight per 100 parts by weight of (a) of an electroconductive carbon
black, wherein the composition has an Izod notched impact strength of more
than 15 kJ/m.sup.2 (measured in accordance with ISO 180/1A) and a volume
resistivity of less than 10.sup.6 Ohm.multidot.cm (measured on the narrow
parallel portion of multipurpose test specimen type A according to ISO
3167 with a length of about 70 mm obtained by breaking off both ends of
the test specimen, molded as described in ISO 294 for dumb-bell bars, the
fracture surface of both ends being coated with a silver paint and the
resisitivity being measured between the silver painted surfaces with an
electrical multimeter).
More preferably the compositions of the invention have a volume resistivity
of less than 5.multidot.10.sup.5 Ohm.multidot.cm, most preferred of
between 5.multidot.10.sup.3 and 5.multidot.10.sup.5 Ohm.multidot.cm. The
concentration of electroconductive carbon black is preferably between 2
and 5 parts by weight.
The thermoplastic compositions may further comprise additional additives.
The invention also relates to articles formed out of the compositions of
the invention.
The invention further relates to a process for the manufacture of the
thermoplastic compositions according to the invention; to a process for
coating objects electrostatically and for the electrostatically coated
objects so obtained.
2. Description of the Related Art
The incorporation of electroconductive carbon blacks in thermoplastic
compositions is generally known. Electroconductive carbon blacks may be
added to give objects made out thermoplastic compositions antistatic
properties or even electroconductive properties. Usually they are added to
change the surface resistivity of such objects only.
JP-A-92-165 939 describes blends of 100 parts of a thermoplastic resin,
which can be a polyphenylene, to which have been added 0.01-5 parts of a
polyamide and 0.1-30 parts electroconductive carbon black. The blends have
an Izod impact strength of 4.0 kg.multidot.cm/cm and have a low SO.sub.2
generation.
The incorporation of electroconductive carbon blacks in thermoplastic
composition usually results in lowering the mechanical properties like
strength, in particular the impact strength. Upon increasing the content
of electroconductive carbon black as may be required to obtained the
desired surface resistivity the mechanical properties usually deteriorate
further.
SUMMARY OF THE INVENTION
It has now been found that in compatibilized polyphenylene ether-polyamide
base resin compositions it is possible to obtain the desired resistivity
values at lower electroconductive carbon black concentrations by following
a special process for the preparation of such compositions. The process
results in new compositions having a unique combination of properties:
good impact strength, good flow and good (low) resistivity values.
The new process of the invention for the manufacture of the thermoplastic
compositions of the invention comprises at least the following two steps
in the indicated order:
1. manufacture of a compatibilized polyphenylene ether-polyamide base resin
and
2. incorporation of the electroconductive carbon black in the
compatibilized polyphenylene ether-polyamide base resin.
The process of the invention makes it possible to obtain the claimed
compositions. In addition the process has the advantage that it is
possible to obtain a more consistent production process i.e. the
properties of the prepared composition in particular the volume
resistivity hardly varies over time when all processing conditions remain
the same. Other known processes for the preparation of blends with the
same overall composition result in products with quite different volume
resistivity.
In the second step of the above indicated process the electroconductive
carbonblack is preferably incorporated into the polyphenylene ether
polyamide base resin after the base resin has been brought into a hot
molten state of at least 300 degrees Centigrade.
The electroconductive black can be added as such or in the form of a master
batch comprising a polymer and the electroconductive carbon black.
The two essential steps of the claimed process of the invention can be
performed very well by means of two compounding steps, for example two
extrusion steps. Said two extrusion steps can be combined in one extruder
with a side stream supply.
It is one object of the invention to provide polyphenylene ether-polyamide
compatibilized base resin compositions comprising electroconductive carbon
blacks, which are suitable for making objects thereof by conventional
molding processes, which objects can be easily coated by common
electrostatic coating processes.
It has been found that the suitability for electrostatic coating is more
directly related with the volume resistivity of the composition than with
the surface resistivity. The surface resistivity may vary for compositions
which are equally well suitable for electrostatic coating processes.
It is therefore preferred in the invented process for the manufacture of
the compositions of the invention to monitor the suitability of the
manufactured compositions for electrostatic coating by measuring the
volume resistivity.
Similarly in the process of electrostatically coating objects made out of
the composition of the invention it is preferred to coat objects made out
of a composition with a predetermined volume resistivity, preferably of
between 5.multidot.10.sup.3 and 5.multidot.10.sup.5 Ohm.multidot.cm.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The thermoplastic compositions of the invention comprise at least the
following two constituents:
A) a compatibilized polyphenylene ether-polyamide base resin and
B) an electroconductive carbon black in the quantity as indicated in the
claims.
The compatibilized component and the composition may further comprise usual
additives, like agents to improve the impact strength, reinforcing fibers,
stabilizers, dyes, pigments, polyolefines, lubricants.
A. Compatibilized polyphenylene ether-polyamide base resin.
The compatibilized polyphenylene ether-polyamide base resin comprises a
polyphenylene ether (a.sub.1) and a polyamide (a.sub.2). The preferred
quantities are 10 to 90 weight percent polyphenylene ether (a.sub.1) and
90 to 10 weight percent polyamide (a.sub.2), based upon the weight of
(a.sub.1) and (a.sub.2) together. More preferred the polyamide constitutes
the continuous phase and is present in a quantity of greater than 35
weight percent of the compatibilized base resin (A).
Preferred polyphenylene ether resins (PPE) and polyamide resins as well as
means for providing compatibilized combinations thereof are described
below.
In general it is desirable that the polyamide component comprises a
continuous phase in the overall composition and, therefore, typically at
least 35 percent by weight of the total PPE-polyamide-composition will be
comprised of the polyamide component.
Polyphenylene ethers are a well known class of compounds sometimes referred
to as polyphenylene oxides. Examples of suitable polyphenylene ethers and
processes for their preparation can be found in U.S. Pat. Nos. 3,306,874;
3,306,875; 3,257,357; and 3,257,358. Compositions of the present invention
will encompass homopolymers, copolymers and graft copolymers obtained by
the oxidative coupling of phenolic compounds. The preferred polyphenylene
ethers used as base resins in compositions of the present invention will
be comprised of units derived from 2,6-dimethyl phenol. Also contemplated
are PPE copolymers comprised of units derived from 2,6-dimethyl phenol and
2,3,6-trimethyl phenol.
A particularly useful PPE would be poly(2,6-dimethyl-1,4-phenylene ether)
having an intrinsic viscosity (I.V.) greater than approximately 0.10 dl/g
as measured in chloroform at 25.degree. C. The I.V. will typically be
between 0.25 and 0.6 dl/g.
The polyamide resins useful in the practice of the present invention are a
generic family of resins known as nylons, characterized by the presence of
an amide group (--CONH--). Nylon-6 and nylon-6,6 are the generally
preferred polyamides and are available from a variety of commercial
sources. Other polyamides, however, such as nylon-4, nylon-12, nylon-6,10,
nylon 6,9 or others such as the amorphous nylons may be useful for
particular polyphenylene ether-polyamide applications.
The polyamides can be provided by a number of well known processes.
Nylon-6, for example, is a polymerization product of caprolactam.
Nylon-6,6 is a condensation product of adipic acid and
hexamethylenediamine. A nylon-6,6 having an average molecular weight of
approximately 10,000 is especially preferred for many useful polyphenylene
ether-polyamide thermoplastic applications. Preferred polyamides will
typically have a relative viscosity of at least 35, in accordance with
ASTM Test Method D789.
In preferred embodiments of the present invention, a compatibilizing agent
may be employed in the preparation of the composition. The two-fold
purpose for using compatibilizing agents is to improve, in general, the
physical properties of the polyphenylene ether-polyamide resin, as well as
to enable the use of a greater proportion of the polyamide component. When
used herein, the expression "compatibilizing agent" refers to those
polyfunctional compounds which interact with either the polyphenylene
ether, the polyamide, or both. This interaction may be chemical (e.g.
grafting) or physical (e.g. affecting the surface characteristics of the
dispersed phases). In either instance the resulting polyphenylene
ether-polyamide composition appears to exhibit improved compatibility,
particularly as evidenced by enhanced impact strength, mold knit line
strength and/or elongation. As used herein, the expression "compatibilized
polyphenylene ether-polyamide base resin" refers to those compositions
which have been physically or chemically compatibilized with an agent as
discussed above, as well as those compositions which are physically
compatibitible without such agents, as taught in U.S. Pat. No. 3,379,792.
Examples of the various compatibilizing agents that may be employed in the
practice of the present invention include: a) liquid diene polymers, b)
epoxy compounds, c) oxidized polyolefin wax, d) quinones, e) organosilane
compounds and f) polyfunctional compounds as described hereinafter.
Liquid diene polymers (a) suitable for use herein include homopolymers of a
conjugated diene with at least one monomer selected from the group
consisting of other conjugated dienes; vinyl monomer, e.g. styrene and
alpha-methyl styrene; olefins, e.g. ethylene, propylene, butene-1,
isobutylene, hexene-1, octene-1 and dodecene-1, and mixtures thereof,
having a number average molecular weight of from 150 to 10,000 preferably
150 to 5,000. These homopolymers and copolymers can be produced by the
methods described in, for example, U.S. Pat. Nos. 4,054,612; 3,876,721 and
3,428,699 and include, among others, polybutadiene, polyisoprene,
poly(1,3-pentadiene), poly(butadiene-isoprene), poly(styrene-butadiene),
polychloroprene, poly(butadiene-alpha methylstyrene),
poly(butadiene-styrene-isoprene), poly(butylene-butadiene) and the like.
Epoxy compounds (b) suitable for use in the practice of the present
invention include: (1) epoxy resins produced by condensing polyhydric
phenols (e.g. bisphenol-A, tetrabromobisphenol-A, resorcinol and
hydroquinone) and epichlorohydrin; (2) epoxy resins produced by condensing
polyhydric alcohols (e.g. ethylene glycol, propylene glycol, butylene
glycol, polyethylene glycol, polypropylene glycol, pentaerythritol and
trimethylolethane and the like) and epichlorohydrin, (3)
glycidyletherified products of monohydric alcohols and monohydric phenols
including phenyl glycidylether, butyl glycidyl ether and cresyl
glycidylether; (4) glycidyl derivates of animo compounds for example, the
diglycidyl derivate of aniline, and (5) epoxidized products of higher
olefinic or cycloalkene, or natural unsaturated oils (e.g. soybean) as
well as of the foregoing liquid diene polymers.
Oxidized polyolefin waxes (c) are well known and a description thereof and
processes for the production of the same are found in U.S. Pat. Nos.
3,822,227 and 3,756,999 and German Patent Publications 3,047,915 and
2,201,862.
Generally, these are prepared by an oxidaton or suspension oxidation of
polyolefin. An especially preferred polyolefin wax is "Hoechst Wachs".
Quinone compounds (d) suitable for use herein are characterized as having
in the molecule of the unsubstituted derivative at least one 6 membered
carbon ring; at least two carbonyl groups in the ring structure, both of
which may be in the same or, if more than one ring, different rings,
provided that they occupy positions corresponding to the 1,2- or
1,4-orientation of the monocyclic quinone; and at least two carbon-carbon
double bonds in the ring structure, said carbon-carbon double bounds and
carbonyl carbon-carbon double bonds in the ring structure, said
carbon-carbon double bonds and carbonyl carbon-oxygen double bonds being
conjugated with respect to each other. Where more than one ring is present
in the unsubstituted quinone, the rings may be fused, non-fused or both:
non-fused rings may be bound by a direct carbon-carbon double bond or by a
hydrocarbon radical having conjugated unsaturation such as .dbd.C--C.dbd..
Substituted quinones are also within the scope of the present invention.
The degree of substitution; where substitution is desired, may be from one
to the maximum number of replaceable hydrogen atoms. Examplary of the
various substituents that may be present on the unsubstituted quinone
structures include halogen, e.g. chlorine, bromine, flourine, etc.
hydrocarbon radicals including branched and unbranched, saturated and
unsaturated alkyl, aryl, alkyl aryl and cycloalkyl radicals and
halogenated derivatives thereof; and similar hydrocarbons having hetero
atoms therein, particularly oxygen, sulfur or phosphorous and wherein the
same connects the radical to the quinone ring (e.g. oxygen link).
As examples of the various quinones there may be mentioned 1,2- and
1,4-benzoquinone; 2,6-diphenyl quinone; tetramethyldiquinone; 2,2'- and
4,4'-diphenoquinone; 1,2-, 1,4- and 2,6-naphthoquinone; chloranils;
2-chloro-1,4-benzoquinone; 2,6-dimethyl benzoquinone and the like.
Organosilane compounds (e) suitable as compatibilizing agents are
characterized as having in the molecule (a) at least one silicon atom
bonded to a carbon through an oxygen link and (b) at least one
carbon-carbon double bond or carbon-carbon triple bond and/or a functional
group selected from the group consisting of an amine group or a mercapto
group provided that the functional group is not directly bonded to the
silicon atom.
In such compounds, the C--O--Si component is generally present as an
alkoxyl or acetoxy group bonded directly to the silicon atom, wherein the
alkoxy or acetoxy group generally has less than 15 carbon atoms and may
also contain hetero atoms (e.g. oxygen). Additionally, there may also be
more than one silicon atom in the compound, such multiple silicon atoms,
if present, being linked through an oxygen link (e.g. siloxanes), a
silicon bond; or a bifunctional organic radical (e.g. methylene or
phenylene groups).
Examples of suitable organosilane compounds include: gamma amino
propyltriethoxy silane, 2-(3-cyclohexanyl)ethyl trimethoxy silane;
1,3-divinyl tetraethoxy silane; vinyl tris-(2-methoxyethoxy)silane;
5-bicycloheptenyl triethoxy silane and gamma mercapto propyl trimethoxy
silane.
Polyfunctional compounds (f) which may be employed as compatibilizer in the
practice of the present invention are of three types. The first type of
polyfunctional compounds are those having in the molecule both (a) a
carbon-carbon double bond or a carbon-carbon triple bond and (b) at least
one carboxylic acid, acid anhydride, acid halide, anhydride, acid halide
anhydride, acid amide, acid ester, imide, amino, or hydroxy group.
Examples of such polyfunctional compounds include maleic acid; maleic
anhydride; fumaric acid; citraconic acid; itatonic acid; maleimide; maleic
hydrazide; reaction products resulting from a diamine and maleic
anhydride, maleic acid, fumaric acid, etc.; dichloro maleic anhydride;
maleic acid amide; unsaturated dicarboxylic acids (e.g. acrylic acid,
butenoic acid, methacrylic acid, t-ethylacrylic acid, pentenoic acid);
decenoic acids, undecenoic acids, dodecenoic acids, linoleic acid, etc.);
esters, acid amides or anhydrides of the foregoing unsaturated carboxylic
acids; unsaturated alcohols (e.g. alkyl alcohol, crotyl alcohol, methyl
vinyl carbinol, 4-pentene-1-ol, 1,4-hexadiene-3-ol, 3-butene-1,4-diol,
2,5-dimethyl-3-hexene-2,5-diol and alcohols of the formula C.sub.n
H.sub.2n-5 OH, C.sub.n H.sub.2n-7 OH and C.sub.n H.sub.2n-9 OH, wherein n
is a positive integer up to 30), unsaturated amines resulting from
replacing from replacing the --OH group(s) of the above unsaturated
alcohols with NH.sub.2 groups; and functionalized diene polymers and
copolymers. Of these, one of the preferred compatibilizing agents for
compositions of the present invention is maleic anhydride. It is possible
to prereact this type of compatibilizers with the polyphenylene ethers of
the compositions.
The second group of polyfunctional compatibilizer compounds suitable for
use herein are charaterized as having both (a) a group represented by the
formula (OR) wherein R is hydrogen or an alkyl, aryl, acyl or carbonyl
dioxy group and (b) at least two groups each of which may be the same or
different selected from carboxylic acid, acid halide, acid anhydride,
anhydride, acid halide anhydride, acid ester, acid amide, imido, amino and
salts thereof. Typical of this group of compatibilizers are the aliphatic
polycarboxylic acids, acid esters and acid amides represented by the
formula:
(R.sup.I O).sub.m R(COOR.sup.II).sub.n (CONR.sup.III.sub.R.sup.IV).sub.s
wherein R is a linear or branched chain, saturated aliphatic hydrocarbon of
from 2 to 20, preferably 2 to 10, carbon atoms; R.sup.I is selected from
the group consisting of hydrogen or an alkyl, aryl, acyl or carbonyl dioxy
group of 1 to 10, preferably 1 to 6, most preferably 1 to 4, carbon atoms,
especially preferred is hydrogen; each R.sup.II is independently selected
from the group consisting of hydrogen or an alkyl or aryl group from 1 to
20 carbon atoms, preferably from 1 to 10 carbon atoms; each R.sup.III and
R.sup.IV is independently selected from the group consisting essentially
of hydrogen or an alkyl or aryl group of from 1 to 10, preferably from 1
to 6, most preferably 1 to 4, carbon atoms; m is equal to 1 and (n+s) is
greater than or equal to 2, preferably equal to 2 or 3, and n and s are
each greater than or equal to zero and wherein (OR.sup.I) is alpha or beta
to a carbonyl group and at least two carbonyl groups are seperated by 2 to
6 carbon atoms. Obviously, R.sup.I, R.sup.II, R.sup.III and R.sup.IV
cannot be aryl when the respective substituent has less than 6 carbon
atoms.
Illustrative of suitable polycarboxylic acids there may be given citric
acid, malic acid, and agaricic acid; including the various commercial
forms thereof, such as for example, the anhydrous and hydrated acids. Of
these, citric acid is another of the preferred compatibilizing agents.
Illustrative of acid esters useful herein include for example, acetyl
citrate and mono- and/or di-stearyl citrates and the like. Suitable acid
amides useful herein include for example N,N'-diethyl citric acid amide;
N-phenyl citric acid amide; N-dodecyl citric acid amide; N,N'-didodecyl
citric acid amide and N-dodecyl malic acid present invention. Especially
preferred derivates are the salts thereof, including the salts with amines
and/preferably, the alkali and alkaline metal salts. Examplary of suitable
salts include calcium malate, calcium citrate, potassium malate and
potassium citrate.
The third group of polyfuntional compatibilizer compounds suitable for use
herein are characterized as having in the molecule both (a) an acid halide
group, most preferably an acid chloride group and (b) at least one
carboxylic acid, carboxylic acid anhydride, acid ester or acid amide
group, preferably a carboxylic acid or carboxylic acid anhydride group.
Exemplary of compatibilizers within this group there may be given
trimellitic anhydride acid chloride, chloroformyl succinic anhydride,
chloro formyl succinic acid, chloroformyl glutaric anhydride, chloroformyl
glutaric acid, chloroacetyl succinic anhydride, chloroacetylsuccinic acid,
trimellitic acid chloride and chloroacetyl glutaric acid. Among these,
trimellitic anhydride acid chloride is preferred. Furthermore, it is
especially preferred that compatibilizers of this group be prereacted with
at least a portion of the polyphenylene ether whereby the compatibilizing
agent is a PPE-functionalized compound.
Each of the foregoing compatibilizing agents are more fully described in
U.S. Pat. Nos. 4,315,086 and 4,642,358; and European Patent Application
No. 04640.
The foregoing compatibilizing agents may be used alone or in any
combination of one another. Furthermore, they may be added directly to the
melt blend or precompounded with either or both the polyphenylene ether
and polyamide as well as with other resinous materials employed in the
preparation of the compositions of the present invention. With many of the
foregoing compatibilizing agents, particularly the polyfunctional
compounds, even greater improvement in compatibility is found where at
least a portion of the compatibilizing agent is precompounded with all or
part of the polyphenylene ether. It is believed that such precompounding
may cause the compatibilizing agent to react with the polymer and,
consequently, functionalize that polymer as noted above for example, the
polyphenylene oxide may be precompounded with trimellitic anhydride acid
chloride to form an anhydride functionalized polyphenylene ether which has
improved compatibility with the polyamide compared to a non-functionalized
ether.
Where the compatibilizing agent is employed in the preparation of the
compositions of the present invention, the initial amount used will be
dependent upon the specific compatibilizing agent chosen and the specific
polymeric system to which is added.
It is possible to use in the composition according to the invention any
other known compatibilisation system. Other systems have been described
for example in U.S. Pat. No. 4,866,114.
Where chemical resistance is a desirable property of the thermoplastic
resin, it will ordinarily be necessary that the polyamide resin form a
continuous phase of the resin composition. Therefore, to avoid a phase
inversion whereby the polyamide phase is discontinuous, the preferred
compositions of the present invention will be comprised of a polyamide
resin in an amount equal to or greater than approximately 35 percent by
weight of the total base resin composition.
It is possible to incorporate in the composition according to the invention
one or more impact modifiers. All impact modifiers as generally used for
compositions comprising a polyphenylene ether, a polyamide or a
combination of a polyphenylene ether and a polyamide can be used.
Particularly suitable are the socalled blockcopolymers, like triblock
copolymers and diblockcopolymers.
A variety of useful polyphenylene ether-polyamide compositions can be
provided which include varying amount of the impact modifier. Typically,
improved properties, especially regarding the ductile behavior of the
plastic, will be noted when 1 to 30 parts by weight of an impact modifier
are utilized per 100 parts of the polyphenylene ether and polyamide
components taken together.
The diblock or triblock copolymer rubber additive which may be used in
compositions of the present invention is a thermoplastic rubber comprised
of one or two alkenyl aromatic blocks which are typically styrene blocks
and a rubber block e.g. a butadiene block which may be partially
hydrogenated.
The thermoplastic composition of the invention may comprise fillers like
glass fibers or talc.
The polymer composition according to the invention may further comprise at
least one flame retardant agent.
All patents and patent applications mentioned above are incorporated herein
by reference.
The invention will be further illustrated by the following examples.
EXAMPLES
Preparation of Compatibilized Polyphenylene Ether Polyamide Blend
A polyphenylene ether derived from 2,6-dimethyl phenol with an intrinsic
viscosity of 40 ml/g (as measured in chloroform at 25.degree. C.) and
citric acid were introduced together with two impact modifiers and
stabilizers at the throat of a WP 28 compounder with a co-rotating twin
screw; downstream in the compounder a polyamide 6,6 with a viscosity
number of 148 ml/g (measured according to ISO 307 in sulphuric acid) was
added. The compounding conditions were such that an average temperature of
310.degree. C. was maintained.
The overall composition of this blend was about 36% by weight of the
polyphenylene ether, about 0.7% by weight citric acid and about 48% by
weight of polyamide 6,6, about 8% by weight of a first blockcopolymer a
diblock copolymer with a saturated olefin rubber, being
ethylene/propylene, as elastomeric block and a thermoplastic polymer,
being styrene, as second block and about 7% by weight of a second block
copolymer a triblock copolymer with a saturated olefin rubber, being
ethylene/butylene, as elastomeric midblock and a thermoplastic polymer,
being styrene, as other blocks and 0.06 inorganic iodine stabilizers.
Comparative Experiments 1 and 2
In a first experiment a compatibilized polyphenylene ether-polyamide blend
was prepared as described above. In a second experiment a comparable
composition was prepared with about 3.5% by weight of an electroconductive
carbon black (EC 600JD of AKZO). This composition was prepared in a
similar way as described above with one difference: carbon black was added
at the throat of the extruder together with the polyphenylene ether.
The obtained extrudates were pelletised. The melt viscosity (according to
ISO 1133), the Izod notched impact strength (according to ISO 180/1A) and
the Volume resistivity were determined of the compatibilized polyphenylene
ether-polyamide resin blend with and without carbon black. All experiments
were repeated several times under almost identical conditions.
The volume resistivity was determined on the narrow parallel portion of
injection molded multipurpose test specimen according to ISO 3167. Said
test specimen were molded as described in ISO 294 for dumb-bell bars with
an injection molding machine (barrel temp. 280 degrees C.; mold
temperature 80 degrees C.; at normal injection speed). Both ends of the
test specimen were broken off so as to obtain a portion with a uniform
cross section of 10.times.4 mm and a length of about 70 mm with a
fractured surface at both ends. The fracture surface at both ends was
coated with a silver paint and the volume resistivity was measured between
both fractured surfaces with an electrical multimeter. The broken off
specimen had a length of about 70 mm. It is essential that fractured
surfaces and not surfaces obtained by cutting with a knife or sawing and
the like are used.
The results were as follows (Table A):
TABLE A
______________________________________
Second Experiment
First Experiment
with about 3.5% by
Without electroconductive
weight electroconductive
Properties
carbon black carbon black
______________________________________
Izod notched
50 5
impact (kJ/m.sup.2)
Melt viscosity at
230 300
1500 s.sup.-1,
282.degree. C. (Pa .multidot. s)
Volume resis-
10.sup.13 or above
10.sup.5 -10.sup.9 *
tivity Ohm .multidot. cm.
______________________________________
*variation found between ten batches run at practically identical
extrusion conditions.
As can be seen the Izod notched impact strength drops considerably upon
addition of 3.5% by weight of electroconductive carbon black. The melt
viscosity increases to a value which is too high for a lot of
applications. It is further difficult to obtain values for the volume
resistivity in a consistent way.
Experiment in Accordance with the Invention (Fourth Experiment) and One
Further Comparative Experiment (Third Experiment)
In a third experiment (comparative) an electroconductive carbon black was
added in the compounder together with the polyamide. All other conditions
and components were the same as in the first experiment.
In a fourth experiment (according to the invention) a composition was first
prepared without any electroconductive carbon black in the way and with
the composition as described for the first experiment. The so obtained
composition was pelletized. The pellets were reintroduced in the
compounder. During this second run through the compounder
electroconductive carbon black was introduced through the downstream side
feeder of the compounder at a point were the composition had reached a
temperature of about 300 degrees Centrigrade. All experiments were
repeated several times under almost identical conditions.
The obtained results (together with the results of the previously described
first experiment) are represented in the following table B.
TABLE B
______________________________________
Fourth Experiment
Third Experiment
Invention
First Comparative 3.0% by weight
Experiment 3.5% by weight
electroconduc-
Comparative
electroconduc-
tive carbon
Without elec-
tive carbon black added in
troconductive
black added second
Properties
carbon black
dry extrusion step
______________________________________
Izod notched
50 15 20
impact (kJ/m.sup.2)
Melt viscosity
230 300 250
at 1500 s.sup.-1,
282.degree. C.
(Polyamide .multidot. s)
Volume resisti-
10.sup.13 or above
10.sup.6 -10.sup.9 *
10.sup.4 -10.sup.5 *
vity Ohm .multidot. cm
______________________________________
*variation found between at least 15 batches run at practically identical
extrusion conditions.
As can be seen from table B the impact strength of the composition of the
invention (fourth experiment) is better than the impact strength of the
compositions of the third experiment (comparative) with carbon black. In
the composition of the invention the variation in volume resistivity from
batch to batch was much smaller (for practical purposes negligible) as
compared to the values found for the composition of the third experiment.
In the fourth experiment the melt viscosity has a reasonable value, much
better than the value of the third experiment.
It is further remarkable that with the process (of the invention) a product
with a lower volume resistivity is obtained at an electroconductive carbon
black concentration of 3.0% by weight lower than with the comparative
process at 3.5% by weight electroconductive carbon black.
The third experiment was run at conditions only slightly different from the
conditions of the fourth experiment. In the third experiment the carbon
black was added before complete preparation of the compatibilized
polyphenylene ether-polyamide blend. In the fourth experiment it was added
after the preparation of this blend. This small difference resulted in
different properties of the obtained blends as discussed above.
Electrostatic Painting
With the process of the invention several compositions were prepared with
different values for the volume resistivity. This was possible by varying
the concentration of the electroconductive black. Discs (101 mm diameter;
3.2 mm thickness) were molded out of the prepared compositions. The discs
with one and the same volume resistivity may have varying surface values.
Upon determination of the suitability of the discs for coating by
convential electrostatic spray coating it was found that discs with one
and the same volume resistivity were equally well suitable regardless of
the surface resistivity. Similarly discs with about the same surface
resistivity but with a different volume resistivity showed a different
behaviour as to their suitability for electrostatic spray coating. With
this finding it has bcome possible to control electrostatic spray coating
better by controlling the volume resistivity rather than the surface
resistivity.
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